Loss of power with new cam

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mtpierson

mtpierson

65 Dart GT Convertible
Joined
Mar 9, 2012
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Location
Spotsylvania VA
Installed a Competition Cam as part of initial rehab of newly purchased 1965 Dart GT with a 1970-1972 Slant Six.

A new timing chain set was also installed and lined up dot to dot at TDC as stated in the instructions.

Ignition is converted to Electronic type.

I have very little background on how vehicle performed before engine was broken down, head/valve job and cam install/carb rebuild were completed. It was running but only droven @ 1/2 mile before loading on a trailer to take home after purchase.


Manufacturer's Part Number: 64-240-4

Product Line: COMP Cams High Energy Camshafts


Summit Racing Part Number: CCA-64-240-4

Cam Style: Mechanical flat tappet

Basic Operating RPM Range: 800-4,500

Intake Duration at 050 inch Lift: 215

Exhaust Duration at 050 inch Lift: 215

Duration at 050 inch Lift: 215 int./215 exh.

Advertised Intake Duration: 252

Advertised Exhaust Duration: 252

Advertised Duration: 252 int./252 exh.

Intake Valve Lift with Factory Rocker Arm Ratio: 0.435 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.435 in.

Valve Lift with Factory Rocker Arm Ratio: 0.435 int./0.435 exh.

Lobe Separation (degrees): 110

Intake Valve Lash: 0.010 in.

Exhaust Valve Lash: 0.012 in.

Timing is set at 5 degrees before TDC. Car drops significantly in power on any incline but seems to run OK, but far from great, on the flat.

The engine is showing about 15" vacuum. No leaks are noticed.

Any ideas out there in FABO land on what I need to check to resolve the loss of power issue?

Carb is recently rebuilt. Engine revs great when transmission in in Park. Carb linkage seems OK. Valve Lash is checked and rechecked.

I've run out of ideas, admit my novice category and am now asking the experts for help.

Thanks
 
The first thing I would do is jack the timing up to at least 12 btc. The factory timing spec was based on real gasoline. Most of us run the timing up until it pings under load then give back 2 degrees.
I have to mention my experience with slant 6 distributers... I've seen more than 1 worn out bad. The point gap/dwell was all over the place. It changed with engine temp too.
Only a reman'd distributer would cure it.
 
If you lined up dot to dot and piston #1 at TDC you are not on the compression stroke. Rotate crank one complete turn and you will be on the compression stroke, I believe your timing marks will be at 12 and 12. You could also just find out where your dizzy is pointing on the compression stroke and make that your #1 plug wire and follow the firing order for slant six.
 
You really cant see 12 and 12 unless you stand that engine up straight again. Putting the 2 dots together only makes life easier. It runs so I doubt its wrong.
 
I was talking relative to the engine. Not the world around us:) If he lined it up dot dot and dropped in the dizzy and made that his #1 it's wrong. Just trying to help the guy out. Those instructions are for a Chevy.
 
Looks to me like the valve adjustment is off, You have the Exhaust Valve Lash: 0.012 in. Shouldn't it be 0.020 ?
 
Johnny Dart said:
Dot to Dot isn't always the answer. Did you degree the cam ?
Click to expand...

I bet he did not, so it's time to pull #1 plug and find his compression stroke
as #1 piston tops out make sure the rotor is pointing to his #1 spark plug.. then start there setting the timing to how much advance the cam wants :coffee2:
 
memike said:
Looks to me like the valve adjustment is off, You have the Exhaust Valve Lash: 0.012 in. Shouldn't it be 0.020 ?
Click to expand...


Specs for the Competition Cam calls for .010 intake and .012 Exhaust so that was my starting point.
 
63dartman said:
If you lined up dot to dot and piston #1 at TDC you are not on the compression stroke. Rotate crank one complete turn and you will be on the compression stroke, I believe your timing marks will be at 12 and 12. You could also just find out where your dizzy is pointing on the compression stroke and make that your #1 plug wire and follow the firing order for slant six.
Click to expand...


Pretty sure we are correct on the compression stroke with #1 aligned with the distributor as expected. Will check again to make sure.
 
RedFish said:
The first thing I would do is jack the timing up to at least 12 btc. The factory timing spec was based on real gasoline. Most of us run the timing up until it pings under load then give back 2 degrees.
I have to mention my experience with slant 6 distributers... I've seen more than 1 worn out bad. The point gap/dwell was all over the place. It changed with engine temp too.
Only a reman'd distributer would cure it.
Click to expand...


OK, Thanks. RPM increased significantly with advance timing. Not sure what that means but will give 12 BTDC a try and see what happens.

Comedy of errors on my part with the forum crowd in the audience trying to help. What a great crowd. Thanks.
 
63dartman said:
If you lined up dot to dot and piston #1 at TDC you are not on the compression stroke. Rotate crank one complete turn and you will be on the compression stroke, I believe your timing marks will be at 12 and 12. You could also just find out where your dizzy is pointing on the compression stroke and make that your #1 plug wire and follow the firing order for slant six.
Click to expand...

63dartman said:
I was talking relative to the engine. Not the world around us:) If he lined it up dot dot and dropped in the dizzy and made that his #1 it's wrong. Just trying to help the guy out. Those instructions are for a Chevy.
Click to expand...

These answers are confusing the issue. Dot to dot, 12/12 have no meaning if the engine RUNS. (That is, the distributor is installed on the compression stroke, and it won't run any other way) So long as the cam drive marks are PROPERLY aligned, one or the other, this is the best you'll do if you haven't or cannot degree the cam. The only meaning this comment has is if the engine will not run, IE is blowing flame out the carb and won't run.

Here's how I see this:

VALVE ADJUSTMENT: How did you accomplish this? How did you rotate the engine? I use what is known as EOIC, which means

You rotate the engine until an EXHAUST valve just starts to OPEN, and you set the intake on that cylinder.

Then you rotate until the INTAKE has opened, and is approaching CLOSED, and set that exhaust valve.

Use the proper feeler, and one .001" or .002" larger for a "go/ no go"

TIMING: Generally, all factory distributors in engines made after 66--68 have crappy "smog" advance curves. You need to SERIOUSLY consider having the dist. recurved or replace it with a performance dist. which has a short curve.

It is also possible, of course, that the dist. has something wrong, IE sticking advance, etc, worn bushings, which enter the picture

You want LOTS of initial timing, much more than factory. You can start with a vacuum gauge, time it for a "peak" in vacuum. Reset idle and mixture (engine up to temp) and recheck timing/ vacuum. You REALLY need to figure out a way to check total mechanical advance, as well as mechanical + vacuum. This is harder on a /6 because of the thin dampener.

Also, how sure are you that your timing marks are accurate? A piston stop is the usual way to check on an assembled engine.

FUEL. It may be possible, here again especially in the case of a "smog" engine, that your carb is now on the ragged end of "lean." In any case, a performance situation, IE hotter cam, exhaust, etc, changes the carb situation.

And of course as others have leaned towards, just how sure ARE you that the cam is actually lined up properly. And here's two other wrenches in the gear works, in this case, sprockets.

1--Some cams are ground advanced or retarded by the cam grinder. I've never figured this out, because if you are not aware, and have not degreed the thing, this alone can cause problems.

2--Some engines (don't know if /6 is one, Ferd did) had later model "smog" cam drives off center by the factory. This is especially a problem if you have a cam like (1) above, the damn thing could be as much as 8* off!!! just from the cam drive and "off ground" cam. I don't have a definite answer on this, I would certainly look into it.
 
Built slants like around 30 degs of total timming. No more than that.
Use a timing light with advance,to set your total timming. Set your total around 28-30.
At this point,whatever your initial is,it is. My guess,working with slant distributors,your
"initial" will now be around 16deg,with your 30deg total.

At this point,don't worry about the curve of the distributor,or vacuum advance.
Plug all the ports for vacuum advance. Once you get the car running decent,then you
can start playing with those.

Go back and check the obvious. Cap,Rotor,Wires, Firing Order of wires,Valve Adjustment,Ect.
I've seen brand new caps,or wires that were crap. Give everything a thorough
inspection.
 
I am assuming your timing set had only one slot on the gears. Many for small blocks have 3 slots so you can choose 4 deg advance, "straight up" or 4 deg retard for the valve timing. Not sure about slant parts. It can be confusing to find the correct marks that go together (dot, triangle, or square I recall). Some even have 7 slots to choose from. However, I think if you set to the wrong mark it wouldn't run at all. I like 4 deg advance since gives better mileage and low end, plus allows 4 deg wear.

On my small block, I was confused because when the dots came together the engine was at TDC compression on #6, not #1 (was at TDC exhaust). I found that is the way it is supposed to be. No idea why. I don't recall ever changing a slant cam.
 
Just to throw in my $0.02, valves should be adjusted with the engine at operating temperature. Adjusting them cold to get it started is a first step, but when it warms up, pop the VC and run the feeler gauges again.

I used that cam in my '70 Duster and absolutely loved it! It certainly has potential.

Using the factory harmonic balancer to set timing can sometimes cause issues. There is a rubber isolator ring that separates the inner from the outer portions of the dampener. If the outer ring slips, timing is off. Using a positive stop in the spark plug hole, you can find TDC and mark it on the balancer. Turn the engine until #1 piston hits the stop, mark the balancer at the 0 mark. Spin the engine the other way until the piston hits again and mark 0 again. TDC will be right in the middle of those 2 marks.

Mike
 
To all participants in this thread Thanks Again for the suggestions. From all the comments this is the plan for now.

12-16 Degrees BTDC timing at idle. This is up from 6 Degrees BTDC now.

.015 to .017 Intake and .017 to .019 Exhaust Valve Timing (0.10 and 0.12 were CAM Specifications that I used currently) adjusted HOT not COLD. I received a specific recommendation for valve adjustment of .016 Intake and .018 Exhaust as the starting point so I am going with a range to work within.

Inspect electronic ignition distributor for proper function.

Recheck TDC accuracy before anything.

Blessing for now is that the car runs, just lack power, especially on any kind of hill. Figure I must be close on CAM install if it is starting easily and running. Slant 6 sounds great at idle and increased RPM under no load. Just punks out when it needs some torque.


Thanks again. Hopefully all to be heard again on this issue is a success story.
 
mtpierson said:
To all participants in this thread Thanks Again for the suggestions. From all the comments this is the plan for now.

12-16 Degrees BTDC timing at idle. This is up from 6 Degrees BTDC now.

Adjust the "Total Timing" not the initial.Total timming should be 28-30 deg.
After setting the "Total",you can see what your initial timing is at idle.
Click to expand...
 
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